Neutron Diffraction Study of Plasticity-Induced Martensite Formation of the Austentic Stainless Steel AISI 321
The elastic and plastic properties of the austenitic matrix and martensitic areas induced during cyclic tensile-compressive loading of low carbon metastable austenitic stainless steel were studied in an in-situ stress rig experiment on the ENGIN instrument are the ISIS pulsed neutron facility. Two sets of samples were prepared from the steel AISI 321. The first set of samples (annealed at 1050°C and quenched in water) was cycled under strain with a strain amplitude of 1% at a frequency of 0.5 Hz. The second set (1070°C/ quenched in air) was cycled under stress control with a stress amplitude of 330 MPa at 5 HZ. The applied stress- elastic strain responses of the austenitic and martensitic phases were obtained by Rietveld and Le Bail refinements of the neutron diffraction spectra. The results of the modified refinements accounting for the elastic anisotropy in polycyrstalline materials under load are also presented. The residual strains were determined for the first set of samples using a noncycled sample as a reference sample.